EP0394500B1 - Process for the production of sintered alpha-alumina bodies - Google Patents
Process for the production of sintered alpha-alumina bodies Download PDFInfo
- Publication number
- EP0394500B1 EP0394500B1 EP89106819A EP89106819A EP0394500B1 EP 0394500 B1 EP0394500 B1 EP 0394500B1 EP 89106819 A EP89106819 A EP 89106819A EP 89106819 A EP89106819 A EP 89106819A EP 0394500 B1 EP0394500 B1 EP 0394500B1
- Authority
- EP
- European Patent Office
- Prior art keywords
- process according
- al2o3
- sintering
- sintered
- carried out
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Revoked
Links
- 238000000034 method Methods 0.000 title claims abstract description 25
- PNEYBMLMFCGWSK-UHFFFAOYSA-N Alumina Chemical compound [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 title claims abstract description 15
- 238000004519 manufacturing process Methods 0.000 title claims description 6
- 229910052593 corundum Inorganic materials 0.000 claims abstract description 16
- 229910001845 yogo sapphire Inorganic materials 0.000 claims abstract description 12
- 238000010335 hydrothermal treatment Methods 0.000 claims abstract description 9
- 239000007858 starting material Substances 0.000 claims abstract description 8
- 239000002253 acid Substances 0.000 claims abstract description 7
- 230000003197 catalytic effect Effects 0.000 claims abstract description 5
- 238000005245 sintering Methods 0.000 claims description 20
- 229910052594 sapphire Inorganic materials 0.000 claims description 15
- 239000000654 additive Substances 0.000 claims description 12
- 238000000227 grinding Methods 0.000 claims description 5
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 claims description 4
- 238000001354 calcination Methods 0.000 claims description 4
- 238000001035 drying Methods 0.000 claims description 4
- 229910017604 nitric acid Inorganic materials 0.000 claims description 4
- 238000003825 pressing Methods 0.000 claims description 4
- 229910052566 spinel group Inorganic materials 0.000 claims description 4
- 239000002245 particle Substances 0.000 claims description 3
- 238000006243 chemical reaction Methods 0.000 claims description 2
- 150000002736 metal compounds Chemical class 0.000 claims description 2
- 229910044991 metal oxide Inorganic materials 0.000 claims description 2
- 150000004706 metal oxides Chemical class 0.000 claims description 2
- 230000000996 additive effect Effects 0.000 claims 1
- 239000003082 abrasive agent Substances 0.000 description 5
- MCMNRKCIXSYSNV-UHFFFAOYSA-N Zirconium dioxide Chemical compound O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 description 4
- 239000010431 corundum Substances 0.000 description 4
- 239000002994 raw material Substances 0.000 description 4
- 239000000126 substance Substances 0.000 description 4
- CPLXHLVBOLITMK-UHFFFAOYSA-N Magnesium oxide Chemical compound [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
- 229910001593 boehmite Inorganic materials 0.000 description 2
- 150000001875 compounds Chemical class 0.000 description 2
- 239000013078 crystal Substances 0.000 description 2
- QDOXWKRWXJOMAK-UHFFFAOYSA-N dichromium trioxide Chemical compound O=[Cr]O[Cr]=O QDOXWKRWXJOMAK-UHFFFAOYSA-N 0.000 description 2
- FAHBNUUHRFUEAI-UHFFFAOYSA-M hydroxidooxidoaluminium Chemical compound O[Al]=O FAHBNUUHRFUEAI-UHFFFAOYSA-M 0.000 description 2
- 229910052759 nickel Inorganic materials 0.000 description 2
- 235000012239 silicon dioxide Nutrition 0.000 description 2
- 238000003980 solgel method Methods 0.000 description 2
- RREGISFBPQOLTM-UHFFFAOYSA-N alumane;trihydrate Chemical compound O.O.O.[AlH3] RREGISFBPQOLTM-UHFFFAOYSA-N 0.000 description 1
- WNROFYMDJYEPJX-UHFFFAOYSA-K aluminium hydroxide Chemical compound [OH-].[OH-].[OH-].[Al+3] WNROFYMDJYEPJX-UHFFFAOYSA-K 0.000 description 1
- 229910052804 chromium Inorganic materials 0.000 description 1
- 229910052681 coesite Inorganic materials 0.000 description 1
- 229910052906 cristobalite Inorganic materials 0.000 description 1
- WMWXXXSCZVGQAR-UHFFFAOYSA-N dialuminum;oxygen(2-);hydrate Chemical compound O.[O-2].[O-2].[O-2].[Al+3].[Al+3] WMWXXXSCZVGQAR-UHFFFAOYSA-N 0.000 description 1
- 239000012153 distilled water Substances 0.000 description 1
- 229910001679 gibbsite Inorganic materials 0.000 description 1
- 239000003966 growth inhibitor Substances 0.000 description 1
- CJNBYAVZURUTKZ-UHFFFAOYSA-N hafnium(IV) oxide Inorganic materials O=[Hf]=O CJNBYAVZURUTKZ-UHFFFAOYSA-N 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 239000011346 highly viscous material Substances 0.000 description 1
- 230000007062 hydrolysis Effects 0.000 description 1
- 238000006460 hydrolysis reaction Methods 0.000 description 1
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 238000010327 methods by industry Methods 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 239000002667 nucleating agent Substances 0.000 description 1
- 230000035939 shock Effects 0.000 description 1
- 150000004760 silicates Chemical class 0.000 description 1
- RMAQACBXLXPBSY-UHFFFAOYSA-N silicic acid Chemical compound O[Si](O)(O)O RMAQACBXLXPBSY-UHFFFAOYSA-N 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 239000000377 silicon dioxide Substances 0.000 description 1
- 239000002002 slurry Substances 0.000 description 1
- 229910052682 stishovite Inorganic materials 0.000 description 1
- 229910052719 titanium Inorganic materials 0.000 description 1
- 230000007704 transition Effects 0.000 description 1
- 229910052905 tridymite Inorganic materials 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
- 229910052725 zinc Inorganic materials 0.000 description 1
- 229910052726 zirconium Inorganic materials 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
- C04B35/01—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics
- C04B35/10—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on aluminium oxide
- C04B35/111—Fine ceramics
- C04B35/1115—Minute sintered entities, e.g. sintered abrasive grains or shaped particles such as platelets
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
- C01F7/00—Compounds of aluminium
- C01F7/02—Aluminium oxide; Aluminium hydroxide; Aluminates
-
- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C09K3/00—Materials not provided for elsewhere
- C09K3/14—Anti-slip materials; Abrasives
- C09K3/1409—Abrasive particles per se
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/60—Particles characterised by their size
- C01P2004/62—Submicrometer sized, i.e. from 0.1-1 micrometer
Definitions
- the present invention relates to a method for producing ⁇ -Al2O3 sintered bodies, wherein an Al2O3 starting material is subjected to a hydrothermal treatment in the presence of catalytic amounts of acid, the product thus obtained is dried, calcined and sintered.
- a preferred application of ⁇ -Al2O3 sintered bodies is their use as an abrasive.
- sintered materials have been known for around 50 years.
- Sintered abrasives based on ⁇ -Al2O3 have become known in recent times, the microcrystalline structure of which has particular advantages in terms of grinding.
- US Pat. No. 4,314,827 describes a microcrystalline abrasive material which is produced using the sol-gel technique at sintering temperatures of approximately 1400.degree.
- a modifying component such as HfO2, ZrO2, MgO, ZnO, CoO, NiO etc. is added.
- EP-A-0 152 768 discloses an abrasive material which is also produced by sintering an alumina hydrate gel.
- finest ⁇ -Al2O3 particles are added to reduce the transition temperature from ⁇ -Al2O3 to ⁇ -Al2O3.
- Other additives of crystal growth inhibitors such as MgO, SiO2, Cr2O3, Fe2O3, ZrO2 can also be used.
- DE-C-3 604 848 describes a process for dispersing alumina-containing raw materials, silicic acid-containing compounds and other additives (compounds of the metals Co, Ni, Cr, Zr, Zn, Si, Ti or Ni) to form a sinterable slip ground, from which an abrasive is produced by gradual drying and sintering at temperatures up to 1700 ° C can, whose corundum crystals have a diameter of less than 5 microns.
- abrasive is produced by gradual drying and sintering at temperatures up to 1700 ° C can, whose corundum crystals have a diameter of less than 5 microns.
- the product obtained in this way also contains approx. 2% silicates, which have no value in terms of grinding performance, and with a crystallite size of less than 5 ⁇ still does not have the fine structure of a substance which was produced by the sol-gel method (crystallite size of less than 0.4 ⁇ ).
- the object of the invention is to provide a method for producing a sintered microcrystalline ⁇ -Al2O3 sintered body (submicron) using an inexpensive raw material which does not have the disadvantages of the prior art methods described.
- the present invention thus relates to a process for the production of ⁇ -Al2O3 sintered bodies, an ⁇ -Al2O3 starting material being subjected to a hydrothermal treatment in the presence Is subjected to catalytic amounts of acid, the product thus obtained is dried, calcined and sintered, chi-Al2O3 being used as the ⁇ -Al2O3 starting material, and sintering additives are added to the product obtained after the hydrothermal treatment.
- the chi-Al2O3 is preferably prepared according to DE-C-2 059 946. Thereafter, the chi-Al2O3 is produced by shock heating in the so-called Schoppe chamber made of aluminum trihydrate (hydrargillite).
- the active oxide thus obtained which is completely boehmite-free and has a surface area of 300 m 2 / g BET (measured by the 1-point nitrogen method), is preferably reacted in an autoclave as an aqueous nitric acid slurry to give a highly viscous mass.
- the amount of sintering additives is 0.2 to 10% by weight, preferably 0.5 to 2% by weight.
- Sintering additives for the purposes of this invention are preferred metal oxides Spinels or metal compounds forming spinels during the reaction conditions.
- Corresponding sintering additives are disclosed, for example, in EP-A-0 200 487.
- ⁇ -Al2O3 seeds are used.
- HNO3 is particularly suitable as an acid during the hydrothermal treatment.
- the final sintering of the products is carried out according to the invention at temperatures between 1200 and 1600 ° C, preferably 1300 to 1380 ° C. It is further preferred to carry out the sintering and the calcination in one step.
- ⁇ -Al2O3 sintered bodies with a density> 95% of the theoretical density and a hardness in the range from 16 to 22 GPa, the crystallite structure of which is in the submicron range.
- 750 g of chi-Al2O3 are concentrated in 3 l of distilled water with 150 ml. Nitric acid stirred in an autoclave at 200 ° C and 20 bar for one hour. The resulting highly viscous substance is dried in a drying cabinet at 80 ° C, then ground, mixed with 7 g of ⁇ -Al2O3 (grain size ⁇ 1 ⁇ ) as a sintering aid and compressed into tablets. The compacts are heated to 1350 ° C. within 6 hours and sintered at this temperature for about 5 hours.
- the compacts are first calcined at temperatures up to 700 ° C, then crushed and then sintered at 1350 ° C.
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Organic Chemistry (AREA)
- Materials Engineering (AREA)
- Ceramic Engineering (AREA)
- Inorganic Chemistry (AREA)
- Geology (AREA)
- Manufacturing & Machinery (AREA)
- Life Sciences & Earth Sciences (AREA)
- Structural Engineering (AREA)
- Compositions Of Oxide Ceramics (AREA)
- Crystals, And After-Treatments Of Crystals (AREA)
- Treatment Of Sludge (AREA)
- Catalysts (AREA)
Abstract
Description
Die vorliegende Erfindung betrifft ein Verfahren zur Herstellung von α-Al₂O₃-Sinterkörpern, wobei ein Al₂O₃-Ausgangsmaterial einer hydrothermalen Behandlung in Gegenwart katalytischer Säuremengen unterzogen wird, das so erhaltene Produkt getrocknet, calziniert und gesintert wird.The present invention relates to a method for producing α-Al₂O₃ sintered bodies, wherein an Al₂O₃ starting material is subjected to a hydrothermal treatment in the presence of catalytic amounts of acid, the product thus obtained is dried, calcined and sintered.
Eine bevorzugte Anwendung von α-Al₂O₃-Sinterkörpern ist deren Einsatz als Schleifmittel.A preferred application of α-Al₂O₃ sintered bodies is their use as an abrasive.
Neben geschmolzenen Korundschleifmitteln sind solche aus gesintertem Material schon seit ca. 50 Jahren bekannt. In der neueren Zeit wurden gesinterte Schleifmittel auf α-Al₂O₃-Basis bekannt, deren mikrokristalline Struktur besondere schleiftechnische Vorteile mit sich brachte.In addition to molten corundum abrasives, sintered materials have been known for around 50 years. Sintered abrasives based on α-Al₂O₃ have become known in recent times, the microcrystalline structure of which has particular advantages in terms of grinding.
So wird in der US-A-4 314 827 ein mikrokristallines Schleifmaterial beschrieben, das über die Sol-Gel-Technik bei Sintertemperaturen von ca. 1400°C hergestellt wird. Als Sinterhilfe wird eine modifizierende Komponente wei HfO₂, ZrO₂, MgO, ZnO, CoO, NiO u.a. zugesetzt.For example, US Pat. No. 4,314,827 describes a microcrystalline abrasive material which is produced using the sol-gel technique at sintering temperatures of approximately 1400.degree. As a sintering aid, a modifying component such as HfO₂, ZrO₂, MgO, ZnO, CoO, NiO etc. is added.
In der EP-A-0 152 768 wird ein Schleifmaterial offenbart, welches ebenfalls durch Sintern eines Aluminiumoxidhydratgels hergestellt wird. Als Keimbildner werden hier zur Herabsetzung der Umwandlungstemperatur von ν-Al₂O₃ in α-Al₂O₃ feinste α-Al₂O₃-Teilchen zugesetzt. Weitere Zusätze von Kristallwachstumshemmern wie MgO, SiO₂, Cr₂O₃, Fe₂O₃, ZrO₂ können ebenfalls verwendet werden.EP-A-0 152 768 discloses an abrasive material which is also produced by sintering an alumina hydrate gel. As nucleating agents, finest α-Al₂O₃ particles are added to reduce the transition temperature from ν-Al₂O₃ to α-Al₂O₃. Other additives of crystal growth inhibitors such as MgO, SiO₂, Cr₂O₃, Fe₂O₃, ZrO₂ can also be used.
Ähnliche Verfahren und Stoffe gehen aus den DE-A-0 024 099, DE-A-3 219 607, US-A-4 518 397, US-A-4 574 003, US-A-4 623 364, EP-A-0 168 606, EP-A-0 200 487, EP-A-0 228 856, EP-A-0 209 084 und EP-A-0 263 810 hervor.Similar processes and substances are disclosed in DE-A-0 024 099, DE-A-3 219 607, US-A-4 518 397, US-A-4 574 003, US-A-4 623 364, EP-A -0 168 606, EP-A-0 200 487, EP-A-0 228 856, EP-A-0 209 084 and EP-A-0 263 810.
Allen vorgenannten Verfahren ist gemeinsam, daß sie über ein Sol-Gel-Verfahren mit feinstdispersem Aluminiumoxidmonohydrat vom Typ des Böhmits durchgeführt werden. Die verhältnismäßig teuren Rohstoffe, welche zum Beispiel über die Hydrolyse von Aluminium-organischen Verbindungen gewonnen werden, und die aufwendige Verfahrenstechnik lassen die Kosten des Sol-Gel-Korundes auf ein Vielfaches der herkömmlichen Korunde ansteigen.All of the above-mentioned processes have in common that they are carried out via a sol-gel process with finely dispersed aluminum oxide monohydrate of the boehmite type. The relatively expensive raw materials, which are obtained, for example, by the hydrolysis of aluminum-organic compounds, and the complex process engineering cause the costs of sol-gel corundum to increase many times over that of conventional corundum.
In der US-A-4 797 139 wird ein Verfahren beschrieben, Aluminiumhydroxid in unter hydrothermalen Bedingüngen Gegenwart katalytischer Säuremengen in mikrokristallinen Böhmit umzusetzen, der als Ausgangsstoff für die Herstellung von alpha-Al₂O₃-Sinterkorpern eingesetzt werden kann.In US-A-4 797 139 a method is described to implement aluminum hydroxide in the presence of hydrothermal conditions catalytic amounts of acid in microcrystalline boehmite, which can be used as a starting material for the production of alpha-Al₂O₃ sintered bodies.
In der DE-C-3 604 848 wird ein Verfahren beschrieben, eine Dispersion aus tonerdehaltigen Rohstoffen, kieselsäurehaltigen Verbindungen und weiteren Zusätzen (Verbindungen der Metalle Co, Ni, Cr, Zr, Zn, Si, Ti oder Ni) zu einem sinterfähigen Schlicker zu vermahlen, aus dem durch stufenweises Trocknen und Sintern bei Temperaturen bis 1700°C ein Schleifmittel hergestellt werden kann, dessen Korundkristalle einen Durchmesser von weniger als 5 µ haben. Es gelingt zwar so, den teuren Rohstoff zu umgehen, allerdings ist man immer noch auf sehr aufwendige Mahlprozesse und hohe Sintertemperaturen angewiesen, um zu dem gewünschten mikrokristallinen Schleifmittel zu gelangen.DE-C-3 604 848 describes a process for dispersing alumina-containing raw materials, silicic acid-containing compounds and other additives (compounds of the metals Co, Ni, Cr, Zr, Zn, Si, Ti or Ni) to form a sinterable slip ground, from which an abrasive is produced by gradual drying and sintering at temperatures up to 1700 ° C can, whose corundum crystals have a diameter of less than 5 microns. Although it is possible to bypass the expensive raw material, one still has to rely on very complex grinding processes and high sintering temperatures in order to obtain the desired microcrystalline abrasive.
Das so erhaltene Produkt enthält außerdem ca. 2 % Silikate, die schleifleistungsmäßig keinen Wert besitzen, und hat mit einer Kristallitgröße kleiner 5 µ immer noch nicht die Feinstruktur eines Stoffes, der über die Sol-Gel-Methode hergestellt wurde (Kristallitgröße kleiner 0,4 µ).The product obtained in this way also contains approx. 2% silicates, which have no value in terms of grinding performance, and with a crystallite size of less than 5 μ still does not have the fine structure of a substance which was produced by the sol-gel method (crystallite size of less than 0.4 µ).
In der Submicron-Struktur wird aber eine Ursache für die besonderen schleiftechnischen Vorteil dieser neuen Schleifmittel gesehen.The submicron structure, however, is seen as a cause for the special technical advantage of these new abrasives.
Aufgabe der Erfindung ist es, ein Verfahren zur Herstellung eines gesinterten mikrokristallinen α-Al₂O₃-Sinterkörpers (Submicron) über einen kostengünstigen Rohstoff aufzuzeigen, welches die beschriebenen Nachteile der Verfahren des Standes der Technik nicht aufweist.The object of the invention is to provide a method for producing a sintered microcrystalline α-Al₂O₃ sintered body (submicron) using an inexpensive raw material which does not have the disadvantages of the prior art methods described.
Es wurde nun gefunden, daß diese Anforderungen erfüllt werden, wenn als Ausgangsmaterial chi-Al₂O₃ eingesetzt wird.It has now been found that these requirements are met if chi-Al₂O₃ is used as the starting material.
Gegenstand dieser Erfindung ist also ein Verfahren zur Herstellung von α-Al₂O₃-Sinterkörpern, wobei ein α-Al₂O₃-Ausgangsmaterial einer hydrothermalen Behandlung in Gegenwart katalytischer Säuremengen unterzogen wird, das so erhaltene Produkt getrocknet, calziniert und gesintert wird, wobei als α-Al₂O₃-Ausgangsmaterial chi-Al₂O₃ eingesetzt wird und dem nach der hydrothermalen Behandlung erhaltenen Produkt Sinteradditive zugesetzt werden.The present invention thus relates to a process for the production of α-Al₂O₃ sintered bodies, an α-Al₂O₃ starting material being subjected to a hydrothermal treatment in the presence Is subjected to catalytic amounts of acid, the product thus obtained is dried, calcined and sintered, chi-Al₂O₃ being used as the α-Al₂O₃ starting material, and sintering additives are added to the product obtained after the hydrothermal treatment.
Bevorzugt wird das chi-Al₂O₃ gemäß der DE-C-2 059 946 hergestellt. Hiernach wird das chi-Al₂O₃ durch Stoßerhitzen in der sogenannten Schoppe-Kammer aus Aluminiumtrihydrat (Hydrargillit) hergestellt. Das so erhaltene aktive Oxid, das vollkommen böhmitfrei ist und eine Oberfläche von 300 m² /g BET (gemessen nach der 1-Punkt-Stickstoff-Methode) aufweist, wird bevorzugt im Autoklaven als wäßrige salpetersaure Aufschlämmung zu einer hochviskosen Masse umgesetzt.The chi-Al₂O₃ is preferably prepared according to DE-C-2 059 946. Thereafter, the chi-Al₂O₃ is produced by shock heating in the so-called Schoppe chamber made of aluminum trihydrate (hydrargillite). The active oxide thus obtained, which is completely boehmite-free and has a surface area of 300 m 2 / g BET (measured by the 1-point nitrogen method), is preferably reacted in an autoclave as an aqueous nitric acid slurry to give a highly viscous mass.
Besonders gute Ergebnisse werden erzielt, wenn die hydrothermale Behandlung bei Temperaturen zwischen 150 und 250°C eine halbe Stunde bis 5 Stunden lang durchgeführt wird. Diese Masse wird getrocknet. Bevorzugt schließt sich dem Trockenschritt ein Feinmahlung, bevorzugt auf eine Korngröße von <1 µm an. Besonders gute Ergebnisse werden erzielt, wenn vor der Calzinierung ein Preßvorgang durchgeführt wird. Der erfindungsgemäße Zusatz der Sinteradditive erfolgt spätestens vor diesem Preßvorgang.Particularly good results are achieved when the hydrothermal treatment is carried out at temperatures between 150 and 250 ° C for half an hour to 5 hours. This mass is dried. The drying step is preferably followed by fine grinding, preferably to a particle size of <1 μm. Particularly good results are achieved if a pressing process is carried out before the calcination. The sintering additives are added according to the invention at the latest before this pressing operation.
Erfindungsgemäß beträgt die Menge der Sinteradditive 0,2 bis 10 Gew.-%, bevorzugt 0,5 bis 2 Gew.-%. Sinteradditive im Sinne dieser Erfindung sind Metalloxide, bevorzugt Spinelle oder während der Reaktionsbedingungen Spinelle bildende Metallverbindungen. Entsprechende Sinteradditive sind z.B. in der EP-A-0 200 487 offenbart.According to the invention, the amount of sintering additives is 0.2 to 10% by weight, preferably 0.5 to 2% by weight. Sintering additives for the purposes of this invention are preferred metal oxides Spinels or metal compounds forming spinels during the reaction conditions. Corresponding sintering additives are disclosed, for example, in EP-A-0 200 487.
In einer bevorzugten Variante des erfindungsgemäßen Verfahrens werden α-Al₂O₃-Keime eingesetzt.In a preferred variant of the method according to the invention, α-Al₂O₃ seeds are used.
Als Säure während der hydrothermalen Behandlung eignet sich besonders HNO₃. Die abschließende Sinterung der Produkte wird erfindfungsgemäß bei Temperaturen zwischen 1200 und 1600°C, vorzugsweise 1300 bis 1380°C, durchgeführt. Es ist weiterhin bevorzugt, die Sinterung und die Calzinierung in einem Schritt durchzuführen.HNO₃ is particularly suitable as an acid during the hydrothermal treatment. The final sintering of the products is carried out according to the invention at temperatures between 1200 and 1600 ° C, preferably 1300 to 1380 ° C. It is further preferred to carry out the sintering and the calcination in one step.
Nach dem erfindungsgemäßen Verfahren gelingt es, α-Al₂O₃-Sinterkörper mit einer Dichte >95 % der theoretischen Dichte und einer Härte im Bereich von 16 bis 22 GPa herzustellen, deren Kristallitstruktur im Submicron-Bereich liegt.According to the process of the invention it is possible to produce α-Al₂O₃ sintered bodies with a density> 95% of the theoretical density and a hardness in the range from 16 to 22 GPa, the crystallite structure of which is in the submicron range.
Im folgenden wird die Erfindung beispielhaft erläutert, ohne daß hierin eine Einschränkung zu sehen ist.The invention is explained below by way of example, without any limitation being seen therein.
750 g chi-Al₂O₃ werden in 3 l destilliertem Wasser mit 150 ml konz. Salpetersäure eine Stunde im Autoklaven bei 200°C und 20 bar gerührt. Der entstandene hochviskose Stoff wird im Trockenschrank bei 80°C getrocknet, anschließend vermahlen, mit 7 g α-Al₂O₃ (Korngröße <1 µ) als Sinterhilfe vermischt und zu Tabletten verpreßt. Die Preßlinge werden innerhalb von 6 Stunden auf 1350°C aufgeheizt und bei dieser Temperatur ca. 5 Stunden gesintert.750 g of chi-Al₂O₃ are concentrated in 3 l of distilled water with 150 ml. Nitric acid stirred in an autoclave at 200 ° C and 20 bar for one hour. The resulting highly viscous substance is dried in a drying cabinet at 80 ° C, then ground, mixed with 7 g of α-Al₂O₃ (grain size <1 µ) as a sintering aid and compressed into tablets. The compacts are heated to 1350 ° C. within 6 hours and sintered at this temperature for about 5 hours.
Eigenschaften des so gewonnenen Stoffes:
- Härte:
- 21 GPa
- Dichte:
- 98 % der Theorie
- Kristallitgröße:
- kleiner 1 µm
- Hardness:
- 21 GPa
- Density:
- 98% of theory
- Crystallite size:
- less than 1 µm
Wie Beispiel 1 werden die Preßlinge zunächst bei Temperaturen bis 700°C calziniert, anschließend zerkleinert und dann bei 1350°C gesintert.As in Example 1, the compacts are first calcined at temperatures up to 700 ° C, then crushed and then sintered at 1350 ° C.
Eigenschaften des so gewonnenen Stoffes:
- Härte:
- 20 GPa
- Dichte:
- 98,2 % der Theorie
- Kristallitgröße:
- kleiner 1 µm
- Hardness:
- 20 GPa
- Density:
- 98.2% of theory
- Crystallite size:
- less than 1 µm
Claims (11)
- A process for production of alpha-Al₂O₃ sintered bodies, wherein an Al₂O₃ starting material is subjected to a hydrothermal treatment in the presence of catalytic amounts of acid and the product so obtained is dried, calcined and sintered, characterized in that chi-Al₂O₃ is used as the Al₂O₃ starting material and sintering additives are added to the product obtained after the hydrothermal treatment.
- A process according to claim 1, characterized in that the hydrothermal treatment is carried out for half an hour to 5 hours at temperatures between 150 and 250 °C.
- A process according to one of claims 1 or 2, characterized in that the drying stage is followed by a fine grinding, preferably to a particle size of <1 µm.
- A process according to one or more of claims 1 to 3, characterized in that before the calcination a pressing operation is carried out.
- A process according to one or more of claims 1 to 4, characterized in that the addition of the sintering additives occurs at the latest before the pressing operation.
- A process according to one or more of claims 1 to 5, characterized in that the amount of the sintering additives is 0.2 to 10 wt%, preferably 0.5 to 2 wt%.
- A process according to one or more of claims 1 to 6, characterized in that the sintering additives are metal oxides, preferably spinels or metal compounds forming spinels under the reaction conditions.
- A process according to one or more of claims 1 to 6, characterized in that α-Al₂O₃ is used as the sintering additive.
- A process according to one or more of claims 1 to 8, characterized in that HNO₃ is used as the acid.
- A process according to one or more of claims 1 to 9, characterized in that the final sintering is carried out at temperatures between 1200 and 1600 °C, preferably 1300 to 1380 °C.
- A process according to one or more of claims 1 to 10, characterized in that the sintering and the calcination are carried out in one step.
Priority Applications (5)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| EP89106819A EP0394500B1 (en) | 1989-04-17 | 1989-04-17 | Process for the production of sintered alpha-alumina bodies |
| AT89106819T ATE86955T1 (en) | 1989-04-17 | 1989-04-17 | PROCESS FOR PRODUCTION OF ALPHA-A1203 SINTERED BODIES. |
| DE8989106819T DE58903831D1 (en) | 1989-04-17 | 1989-04-17 | METHOD FOR PRODUCING ALPHA A1203 SINTER BODIES. |
| CA 2014482 CA2014482A1 (en) | 1989-04-17 | 1990-04-12 | Production of alpha-al 0 sintered bodies |
| JP2096643A JPH02293371A (en) | 1989-04-17 | 1990-04-13 | Sintered object of alpha-al203 |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| EP89106819A EP0394500B1 (en) | 1989-04-17 | 1989-04-17 | Process for the production of sintered alpha-alumina bodies |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| EP0394500A1 EP0394500A1 (en) | 1990-10-31 |
| EP0394500B1 true EP0394500B1 (en) | 1993-03-17 |
Family
ID=8201245
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| EP89106819A Revoked EP0394500B1 (en) | 1989-04-17 | 1989-04-17 | Process for the production of sintered alpha-alumina bodies |
Country Status (3)
| Country | Link |
|---|---|
| EP (1) | EP0394500B1 (en) |
| AT (1) | ATE86955T1 (en) |
| DE (1) | DE58903831D1 (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2001187773A (en) | 2000-01-06 | 2001-07-10 | Mitsubishi Chemicals Corp | Acrylonitrile composition |
| DE10019184A1 (en) * | 2000-04-17 | 2001-10-25 | Treibacher Schleifmittel Gmbh | Production of sintered microcrystalline molded body used as an abrasive body comprises mixing alpha-alumina with a binder and a solvent to form a mixture, extruding the mixture to an extrudate, processing to molded bodies, and sintering |
| RU2229441C1 (en) * | 2002-12-17 | 2004-05-27 | Данчевская Марина Николаевна | Method of preparing fine-grained corundum |
| CN110240492B (en) * | 2018-03-07 | 2020-07-28 | 海加尔(厦门)科技有限公司 | Preparation method of acid-alkali-resistant ceramic separation membrane support |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2915365A (en) * | 1954-06-28 | 1959-12-01 | Pechiney Prod Chimiques Sa | Method of preparing activated alumina from commercial alpha alumina trihydrate |
| US3226191A (en) * | 1965-03-15 | 1965-12-28 | Kaiser Aluminium Chem Corp | Method of producing active alumina and the resulting product |
| CA1267164A (en) * | 1985-12-13 | 1990-03-27 | Harold G. Sowman | Microcrystalline transition metal oxide spinel articles |
| US4797139A (en) * | 1987-08-11 | 1989-01-10 | Norton Company | Boehmite produced by a seeded hydyothermal process and ceramic bodies produced therefrom |
-
1989
- 1989-04-17 EP EP89106819A patent/EP0394500B1/en not_active Revoked
- 1989-04-17 DE DE8989106819T patent/DE58903831D1/en not_active Revoked
- 1989-04-17 AT AT89106819T patent/ATE86955T1/en not_active IP Right Cessation
Also Published As
| Publication number | Publication date |
|---|---|
| EP0394500A1 (en) | 1990-10-31 |
| ATE86955T1 (en) | 1993-04-15 |
| DE58903831D1 (en) | 1993-04-22 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| DE3586779T2 (en) | CERAMIC GRINDING WHEEL. | |
| EP0406847B1 (en) | Sintered material on basis of aluminium oxide, process for its production and its utilisation | |
| DE3587823T2 (en) | Molded ceramic article and process for its manufacture. | |
| DE69214335T2 (en) | Process for the production of colloidal boehmite | |
| DE3586807T2 (en) | METHOD FOR PRODUCING TONER DECODES. | |
| DE19503854C2 (en) | Process for the production of sintered alpha-Al¶2¶O¶3¶ bodies and their use | |
| EP0248788B1 (en) | Microcrystalline abrasive agent and process for its preparation | |
| DE68927106T2 (en) | SMALL PARTICLES AND TABLETS OF ALPHA ALUMINUM OXYD | |
| DE69634164T2 (en) | Aluminum oxide particles with increased dispersibility and plasticity and process for their preparation | |
| EP0263810A2 (en) | Sintered abrasive material based on alpha-alumina | |
| EP0314939B1 (en) | Zirconium oxide powder, process for its preparation and use thereof | |
| EP0105025A1 (en) | Process for the preparation of crystalline aluminium oxide | |
| EP0518106B1 (en) | Partially crystalline transition aluminium oxides, process for their preparation and use thereof for the production of shaped articles which contain substantially gamma alumina | |
| DE4026828C2 (en) | ||
| EP0209084B2 (en) | Process for preparing ceramic polycrystalline abrasives | |
| DE4119183C2 (en) | Sintered composite abrasive article, process for its preparation and its use | |
| DE3786246T2 (en) | METHOD FOR PRODUCING ABRASIVE PARTICLES FROM ALUMINUM OXIDE, ALUMINUM OXINITRIDE, METAL NITRIDE OF THE GROUP - IV-B BY A SOL - GEL - PROCESS. | |
| EP0571865B1 (en) | Sintered composite abrasive grains, method of preparation and use thereof | |
| EP0402686B1 (en) | Process for manufacturing alpha-al2o3 microcrystalline sintered bodies and their use | |
| EP0519159A2 (en) | Polycrystalline sintered abrasive grains of alpha-Al2O3, method of manufacturing them and their use | |
| DE68924707T2 (en) | ABRASIVE GRAIN AND METHOD FOR PRODUCING IT. | |
| EP0394500B1 (en) | Process for the production of sintered alpha-alumina bodies | |
| AT394857B (en) | ABRASIVE GRAIN BASED ON SINTED ALUMINUM OXIDE AND METAL CONTAINERS AND METHOD FOR THE PRODUCTION THEREOF | |
| DE4217721C1 (en) | SINTERED VERBUNDSCHLEIFKORN, METHOD FOR THE PRODUCTION THEREOF AND ITS USE | |
| EP0394501B1 (en) | Process for the production of alpha alumina sintered bodies |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PUAI | Public reference made under article 153(3) epc to a published international application that has entered the european phase |
Free format text: ORIGINAL CODE: 0009012 |
|
| 17P | Request for examination filed |
Effective date: 19890417 |
|
| AK | Designated contracting states |
Kind code of ref document: A1 Designated state(s): AT BE CH DE ES FR GB IT LI NL SE |
|
| 17Q | First examination report despatched |
Effective date: 19920116 |
|
| RAP1 | Party data changed (applicant data changed or rights of an application transferred) |
Owner name: H.C. STARCK GMBH & CO. KG |
|
| GRAA | (expected) grant |
Free format text: ORIGINAL CODE: 0009210 |
|
| AK | Designated contracting states |
Kind code of ref document: B1 Designated state(s): AT BE CH DE ES FR GB IT LI NL SE |
|
| PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: SE Effective date: 19930317 Ref country code: NL Effective date: 19930317 Ref country code: GB Effective date: 19930317 Ref country code: BE Effective date: 19930317 |
|
| REF | Corresponds to: |
Ref document number: 86955 Country of ref document: AT Date of ref document: 19930415 Kind code of ref document: T |
|
| ITF | It: translation for a ep patent filed | ||
| REF | Corresponds to: |
Ref document number: 58903831 Country of ref document: DE Date of ref document: 19930422 |
|
| PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: LI Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES Effective date: 19930430 Ref country code: CH Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES Effective date: 19930430 |
|
| ET | Fr: translation filed | ||
| PG25 | Lapsed in a contracting state [announced via postgrant information from national office to epo] |
Ref country code: ES Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT Effective date: 19930618 |
|
| NLV1 | Nl: lapsed or annulled due to failure to fulfill the requirements of art. 29p and 29m of the patents act | ||
| GBV | Gb: ep patent (uk) treated as always having been void in accordance with gb section 77(7)/1977 [no translation filed] |
Effective date: 19930317 |
|
| PLBI | Opposition filed |
Free format text: ORIGINAL CODE: 0009260 |
|
| REG | Reference to a national code |
Ref country code: CH Ref legal event code: PL |
|
| 26 | Opposition filed |
Opponent name: MINNESOTA MINING AND MANUFACTURING COMPANY Effective date: 19931217 |
|
| PGFP | Annual fee paid to national office [announced via postgrant information from national office to epo] |
Ref country code: DE Payment date: 19940314 Year of fee payment: 6 |
|
| PGFP | Annual fee paid to national office [announced via postgrant information from national office to epo] |
Ref country code: FR Payment date: 19940330 Year of fee payment: 6 |
|
| PGFP | Annual fee paid to national office [announced via postgrant information from national office to epo] |
Ref country code: AT Payment date: 19940418 Year of fee payment: 6 |
|
| RDAG | Patent revoked |
Free format text: ORIGINAL CODE: 0009271 |
|
| STAA | Information on the status of an ep patent application or granted ep patent |
Free format text: STATUS: PATENT REVOKED |
|
| 27W | Patent revoked |
Effective date: 19950414 |
|
| PLAB | Opposition data, opponent's data or that of the opponent's representative modified |
Free format text: ORIGINAL CODE: 0009299OPPO |